The present invention relates to micromechanical I-shaped bulk acoustic resonators (IBARs).
Micromechanical resonators are strong candidates to complement quartz technology in frequency references. Frequency accuracy is a key technological hurdle that must be addressed. Deviations in center frequency can be attributed to material properties and geometry. To address this issue, center frequency trimming by iterative laser ablation and by selective deposition have been proposed. Individually-programmed synthesizers utilizing fractional-N phase lock loops (PLLs) have also been demonstrated. However, a design for manufacturability (DRM) technique employing batch compensation would address the issue at its roots.
The material properties must be consistent and repeatable to enable DFM. Single-crystal silicon (SCS) is the choice material since it is the best controlled and most characterized. Its ideal crystalline nature also has potential for very high Q and minimal aging. For reference, quartz crystal units typically have absolute frequency tolerances up to ±20 ppm. Hence, the applicability of micromechanical resonators is contingent on meeting similar performance metrics.
It would be desirable to have improved micromechanical resonators and fabrication methods. In particular, it would be desirable to have improved micromechanical tapered I-shaped bulk acoustic resonators.